Never heard the Audient and haven't heard the current Duet. Previously, however, I owned the original firewire Duet. I briefly used it for recording LPs, but the Korg MR-1000 DSD recorder was definitely superior, so I archived my LPs with that. To my ears, the Duet had some typical solid state colorations, especially in the treble (roughness) and lower midrange (thin, not fully fleshed out). It did, however, have glorious midrange reproduction. Note that I was using super high end audio equipment for recording and playback. With lesser equipment, the differences between the Duet and Korg would likely have been more subtle and perhaps inaudible. Since I am biased by that experience, I would suggest the Audient...and if you purchase it from Sweetwater or B&H Photo, you can return it if you don't like it. Better yet, buy/try both and return the one you like least.

I got my Apogee Duet Firewire a few years ago.
It was used unit, ant it had become a cheaper because Apogee dropped support for newer MAC OS.
It still works with MAC OS X Sierra (ver. 10.12), I mainly use with my retired, old white plastic Macbook with Firewire 400 port.
I like the unit a lot.
I used it as a Hi-Res audio playback device, with iTunes (yes, iTunes can play Hi-res audio files.) It has a relay switch inside, so when you change sample rate (for instance), it mutes potentially damaging clicking noise.